Is Sheridan County, WY a radon risk area?

EPA places Sheridan County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Sheridan County sits at the 86th percentile nationally for radon potential — above 86 of every 100 rated counties.

How Sheridan County compares

About 32,978 people live in Sheridan County, Wyoming, spread over 2,523.361 square miles. Population density there runs about 13 people per square mile. Rank 442 by population within its EPA zone puts Sheridan County at the 59th percentile among zone peers. Geologically, Sheridan County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Sheridan County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Sheridan County specifically.

Next steps for a home in Sheridan County

Nothing about Sheridan County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Wyoming's state radon program

Sheridan County's test kit answers today; a Airthings radon monitor keeps answering for Sheridan County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Sheridan County's numbers. Whatever zone Sheridan County carries, the zone explainer covers what it does and doesn't tell you about any one house.